CARDIOPULMONARY ADAPTATIONS TO PNEUMONECTOMY IN DOGS .3. VENTILATORY POWER REQUIREMENTS AND MUSCLE STRUCTURE

Static and dynamic mechanical characteristics of the respiratory syste m were measured in five adult foxhounds 6-15 mo after right pneumonect omy (R-PNX) and in five matched foxhounds that underwent right thoraco tomy without pneumonectomy (Sham). In R-PNX dogs, elastic recoil was l ower than that in the left lung of Sham dogs. On exercise, absolute ve ntilatory power requirements of the lung and its components were measu red, i.e., power requirements to overcome elastic and viscous resistan ces of the lung as well as power requirements during inspiration and e xpiration. All components were higher for a given minute ventilation i n R-PNX dogs than in both lungs of Sham dogs. Ventilatory power requir ements after R-PNX were also higher than in three adult foxhounds afte r left PNX stud led previously by the same techniques. After R-PNX, th e mass of the right costal diaphragm and total mass of inspiratory mus cles were greater than in Sham dogs. There were no significant differe nces in ultrastructural features of the costal diaphragm. The unilater al increase in muscle mass is likely the result of chronic elevation a nd stretch of the right costal diaphragm after R-PNX.